Pregnancy Due Date Calculator
Estimate your baby's due date from your last period, conception or IVF transfer, and see your current week, trimester and pregnancy milestones.
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How to use Pregnancy Due Date Calculator
- 1
Open Pregnancy Due Date Calculator on this page. It loads right in your browser.
- 2
Add your file, text or values and adjust the settings.
- 3
Copy the result or download it. Nothing is uploaded or stored.
How to use it: Pregnancy Due Date Calculator
This due date calculator estimates when your baby is due and how far along you are. Use the first day of your last menstrual period (with your usual cycle length), a known conception date, or an IVF embryo transfer date (day 3 or day 5).
Alongside the estimated due date you see your current week and day of pregnancy, the trimester, days to go and a timeline of key milestones: the dating and anatomy scans, glucose screening, the third trimester and full term; each with its own date.
How to use it
- Choose how to calculate: last period, conception or IVF transfer.
- Enter the date (and your average cycle length for the last-period method).
- Read the due date, weeks pregnant, trimester and days to go.
- Scroll the timeline to see the date of each milestone.
How it is calculated
Naegele's rule: due date = first day of the last period + 280 days (40 weeks), adjusted by the difference between your cycle length and 28 days. From conception, add 266 days; from a day-5 transfer, add 261 days (day 3: 263).
Worked example
If your last period started on 1 March and your cycle is 28 days, your due date is 6 December. With a 32-day cycle it moves 4 days later, to 10 December. On 15 May you would be 10 weeks and 4 days pregnant, in the first trimester.
Who uses it
- Expecting parents planning ahead
- Working out your current week of pregnancy
- Planning maternity leave and appointments
- IVF patients dating a pregnancy from transfer
Tips
- An early ultrasound gives the most accurate due date; your doctor may adjust it.
- Only about 4 to 5% of babies are born on their due date: most arrive between 38 and 42 weeks.
- Enter your usual cycle length if it is not 28 days; it shifts the estimate.
Free, private and instant: every calculation runs in your browser, nothing is uploaded or stored, and there is no sign-up or limit. Related calculators: date calculator, age calculator, calorie calculator.
Features
- Last period, conception or IVF method
- Cycle-length adjustment
- Weeks + days pregnant and trimester
- Pregnancy milestone timeline with dates
- Private: nothing is stored
Frequently asked questions
How is the due date calculated?
The standard method adds 280 days (40 weeks) to the first day of your last period, corrected for cycle length. The calculator also works from conception or IVF transfer dates.
How many weeks pregnant am I?
Pregnancy is counted from the first day of your last period, so at conception you are already about 2 weeks pregnant. The calculator shows your current week and day.
How accurate is a due date?
It is an estimate. Most babies are born within two weeks either side; an early ultrasound usually gives the most reliable date.
How do I calculate an IVF due date?
Choose IVF transfer and the embryo age. For a day-5 blastocyst transfer the due date is 261 days after the transfer.
When do the trimesters start?
The first trimester runs to the end of week 12, the second from week 13 to 27 and the third from week 28 until birth.
Is this calculator free and private?
Yes. It is completely free, needs no account and runs entirely in your browser, so the numbers you type are never sent to a server or stored.